| Ionic liquids (IL), or salts that are liquid near room temperature, are finding an ever increasing range of applications. Many of these involve environments where redox and photochemical processes play a key role, such as in dye sensitized solar cells, or the treatment of spent nuclear fuel. Yet little is still known about the details of the fast processes and fate of excess electrons in these materials, and this work attempts to further our understanding of such dynamics in this diverse class of substances.;After the Introduction and Experimental sections, the first chapter reports our first photodetachment experiments in the [Py(+/1,4)][NTf)(-/2)] ionic liquid. Although we later found out that upon further purification this IL does not absorb at the excitation energy that we used, 4.67 eV, and thus the signals we observed could not be due to electrons ejected from the liquid itself but must have originated from some impurity, the transient absorptions and their quenching with an electron scavenger still offer valuable information and is thus presented.;Next, the same kind of experiment but at a higher energy was performed on a homologous series of the same type of liquids: [Py(+/1,3)][NTf(-/2)], [Py(+/1,6)][NTf(-/2)] and [Py(+/1,10)][NTf(-/2)]. Purification of these liquids has shown that the onset of absorption is above ∼ 5.8 eV, and we have had to use 6.2 eV laser pulses. Following absorption of one photon, the characteristic near-IR transients of electrons in these liquids appear and their ultrafast relaxation is followed. Evidence is found that the NTf(-/2) anion undergoes an ultrafast dissociative electron attachment reaction, as it has been predicted theoretically. Ultrafast quenching in the presence of electron scavengers indicates the existence of early very delocalized states of the ejected electron. A competition between electron capture by the NTf(-/2) anions on the one hand, and solvation in some kind of cavity on the other, is proposed as a way to explain the observations.;The injection of electrons into the liquid from another electron donor, I-, is then investigated. It is found that within the accuracy of our experiments the cleavage of the NTf(-/2) anions is suppressed, and that a completely different electron cooling pathway to the same final solvation state is followed. Mechanisms to explain these findings are discussed.;Finally, a set of results performed on a liquid with an anion resistant to reductive cleavage, [Py(+/1,4) ][N(CN)(-/2)], are presented which raise interesting questions on the interpretation of the results in the [Py(+/1, x)] liquids.;Each of the series of experiments mentioned above have also been performed on [Py(+/1,4)][NTf(-/2)], but the results were not in agreement with the trends shown by the other members of the series. We have reasons to believe that the [Py(+/1,4)][NTf(-/2)] liquid contained some impurities that our purification method could not eliminate. Because of this, the results for this liquid are presented in the appendices. |
